SIO Speed up


I have seen and heard several people/programs that seem to to a bit confused about
SIO baud rates and which drives have the fastest baud rate.
I have been playing around with my frequency counter which I will admit isen’t accuret
but it gives a good idea of what the baud rate is.
I have also found bits of information on other 1050 drive upgrades and have formed a
table of sio speeds for varous drives and approxamet baud rates for a PAL system.
This table will be broken into two coloums. The first number is the Hex value placed
into the pokey audio frequency for the command frame. the second is for the data

Cmd data
$28 $28 19120 std rate for all devices except cassette
$28 $10 39000 STD XF551 high speed.
$0A $0A 52000 USD and compatiables. Happy?
$09 $09 57000 Speedy
$28 $06 72000 IndusGT Syncromesh high speed.

Both XF551 and Indus have the high bit (7) set of the command byte for a highspeed
data frame.

I would like to hear from anybody who can add to this or dispute the numbers I have
come up with. Someone with a better frequency counter can make the baudrates more
The hex table except for the speedy part came from SDX.

Of course, having the Fastest baud rate doesn’t make the drive the fastest overall.